Dungeon persistence

Dungeons may be:

• non-persistent, where a level is different every time the user returns to it through an entry point, such as a set of stairs.
• persistent, where once a level is generated it is fixed, and its contents will not change randomly upon re-entry.
• mostly persistent, which is a persistent dungeon that may be slowly re-populated with wandering monsters.

Non-persistent dungeons

In early roguelike games, the non-persistence of dungeons had more to with memory limitations than it did with enhancing gameplay. Thus dungeons in most new roguelikes are not of this variety (Angband being a notable exception).

• The player doesn't have to venture far to come upon a new scenario
• Easy for player to farm previous levels for experience/treasure

Persistent dungeons

Supporting persistent dungeons makes life a little more difficult for the developer since it requires the dungeon state to be loaded and saved between games and, very likely, every time the player moves from one level to the next.

• Items remain in place (can drop stuff off and it will be there if you come back (see Stashing))
• Modification of dungeon (such as digging tunnels or blowing up trees, ect) is permanent
• Realistic
• Sense of accomplishment in exploring an entire level can be attained
• Bleak if a level has been permanently cleared

Mostly persistent

The most complicated type of dungeon from a developer perspective, a mostly persistent dungeon requires code that will determine at what frequency the dungeon should be re-populated, and also to handle the actual re-population.

• Arguably more realistic than the other options
• Makes traversing levels that have been previously cleared more interesting (or perhaps tedious)